Internet Engineering Task Force (IETF) M. Amundsen
Request for Comments: 6573 April 2012
Category: Informational
ISSN: 2070-1721
The Item and Collection Link Relations
Abstract
RFC 5988 standardized a means of indicating the relationships between
resources on the Web. This specification defines a pair of reciprocal
link relation types that may be used to express the relationship
between a collection and its members.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6573.
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Amundsen Informational [Page 1]RFC 6573 The Item and Collection Link Relations April 20121. Introduction
RFC 5988 standardized a means of indicating the relationships between
resources on the Web. This specification defines a pair of reciprocal
link relation types that may be used to express the relationship
between a collection and its members.
These link relation types can be applied to a wide range of use cases
across multiple media types. For example, the 'collection' and
'item' link relation types are used in these media types:
1. OpenSearch 1.1: see Section 4.5.4.1 of [OpenSearch]
2. Maze+XML: see [Maze]
3. Collection+JSON: see [CollectionJSON]
2. Link Relations
The following link relations are defined.
2.1. 'item'
When included in a resource that represents a collection, the 'item'
link relation identifies a target resource that represents a member
of that collection.
For example, if a resource represents a catalog of products, that
same representation may include one or more links to resources that
represent members of that catalog.
<html>
...
<h1>Product Group X Listing</h1>
...
<a href="..." rel="item">View Product X001</a>
<a href="..." rel="item">View Product X002</a>
...
</html>
or, in the case of a Link Header field
Link: <...>; rel="item"; title="View Product X001"
Link: <...>; rel="item"; title="View Product X002"
Amundsen Informational [Page 2]RFC 6573 The Item and Collection Link Relations April 20122.2. 'collection'
When included in a resource that represents a member of a collection,
the 'collection' link relation identifies a target resource that
represents a collection of which the context resource is a member.
For example, if a resource represents a single product in a catalog,
that same representation may include a link to a resource that
represents a product group to which this single product belongs:
<a href="..." rel="collection">Return to Product Group X</a>
or, in the case of a Link Header field
Link: <...>; rel="collection"; title="Return to Product Group X"
Since it is possible that a resource could be a member of multiple
collections, multiple 'collection' link relations may appear within
the same representation:
<a href="..." rel="collection">View other widgets</a>
<a href="..." rel="collection">View all discontinued items</a>